1. Field of the Invention
The present invention relates to and 2-phenoxy-2-pyrrolidin-3-yl-ethylsulfonamide and 2-phenoxy-2-pyrrolidin-3-ylethanesulfonic acid amide compounds having activity as serotonin (5-HT) reuptake inhibitors and, in one embodiment, having the characteristic of being selectively restricted from the central nervous system. The invention also relates to pharmaceutical compositions comprising such compounds, processes, and intermediates for preparing such compounds and methods of using such compounds to treat pulmonary arterial hypertension and other ailments.
2. State of the Art
Progressive increase in pulmonary vascular resistance (PVR) restricts blood flow and causes pulmonary arterial hypertension (PAH), which ultimately leads to right heart failure and death. PAH includes primary pulmonary hypertension and pulmonary hypertension associated with collagen vascular diseases, congenital systemic-to-pulmonary shunts, portal hypertension, and HIV infection. The causes of increased PVR include vasoconstriction and vascular remodeling (increased VSMC proliferation/migration/fibrosis and narrowing of vascular lumen). The goal of therapy is to improve symptoms and exercise capacity, and, ultimately, survival. Current drug therapies include treatment with prostanoids, calcium channel blockers, endothelin receptor antagonists, and PDE-5 inhibitors. Unfortunately, these drugs typically only provide a symptomatic benefit. Therefore, there is an unmet need for drugs that can impact PAH disease progression.
There is preclinical evidence for a role of both serotonin (5-hydroxytrypamine, 5-HT) and the serotonin transporter (SERT) in PAH. SERT is highly expressed in human lung and 5-HT, via interaction with SERT, stimulates proliferation of human pulmonary vascular smooth muscle cells (HPVSM). The proliferative effects of 5-HT are exaggerated in HPVSM from PAH patients. Serotonin selective reuptake inhibitors (SSRIs) have been shown to prevent or reverse PAH in animal models (Zhu et al. (2009) Clinical and Experimental Pharmacology and Physiology 36(8): e1-e5), and the overexpression and deficiency of SERT increases and decreases susceptibility to hypoxia-induced PAH in mice, respectively (Shah et al. (2009) Chest 136(3):694-700).
While there are numerous SSRIs available on the market, most are directed to treating diseases such as depression, anxiety, and other mental health conditions, and thus are designed to primarily enter the central nervous system (CNS). Unfortunately, this CNS activity is often associated with adverse effects such as nausea, sexual distraction, insomnia, somnolence and anxiety. Treatment of diseases such as PAH do not require CNS activity. Therefore, it is desirable to design a therapeutic agent that has SERT inhibition activity yet is peripherally selective, thus potentially avoiding or reducing centrally mediated side effects. This invention is directed to that need.